1. Field of the Invention
The present invention relates to electro-mechanical actuators, and more particularly to a load feedback mechanism to measure small and large loads.
2. Description of Related Art
Throughout history, engineers have invented mechanisms that have had the capability to move objects. One particular category of these mechanisms is referred to as an actuator. Actuators can be designed to move objects in a rotary motion, or in a linear motion. A rotary actuator is simply a gearbox that either increases or decreases the rotational speed of a prime mover, typically a hydraulic motor, an internal combustion engine, a turbine engine, or an electric motor, to provide a desired level of rotational speed and torque at the output of the machine. Some examples of rotary actuators include: gearboxes, transmissions, differentials, hydraulic rotary actuators, and rotary electro-mechanical actuators. Linear actuators are machines designed to provide force and linear displacement to an object. Some examples of linear actuators include: rack and pinion actuators, hydraulic rams, ball screw actuators, and crank arm actuators.
Historically, hydraulic/pneumatic motors and hydraulic/pneumatic rams have been a primary source of power for both linear and rotary actuators. Hydraulic systems offer many advantages to the designer. These advantages include: high power density, accurate position control, low inertia (for high frequency response), and overload protection (via pressure relief valves).
In the last several decades, engineers have started to replace hydraulic/pneumatic actuation systems with electro-mechanical actuation systems. Electro-mechanical actuators offer increased efficiency over their hydraulic and pneumatic counterparts. Electro-mechanical actuators also eliminate the fire hazards and leakage potentials associated with the hydraulic fluids used in hydraulic actuation systems. However, one drawback to the traditional electro-mechanical actuators is they are unable to sense actuator output load across a large operating range, without comprising the actuator's structural stiffness. The traditional load sensor concept has a minimum sensed load capability that is about 5% to 10% of the maximum load.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved actuator systems. There is also a need for such systems that are easy to make and use. The present disclosure provides a solution for these problems.